C. Chanson PPT 17

1. New development in Lithium batteries packaging WRBRF, March 23-24, Berlin C. Chanson PPT 17

2. Li batteries transport: change in requirements • The UN transport regulation is evolving toward new requirements • Initially, safety was based on the “product reliability”, in order to avoid thermal run-away: the manufacturer of products is required to prove the product design and manufacturing quality ( UN 38.3 qualification requirement) • New requirements are coming in addition: the battery should be packaged in order to manage the consequences in case of thermal runaway, which is a complete different concept, requiring packaging specific properties. • Examples: • The recent SP 376, with P908 requiring insulation cushionning • The new requiremenst from ACCAIA and ICAO to qualify packaging limiting the fire propagation in case of Li batteries transport by air.

3. 1-Li batteries transport: cushioning requirement • The packaging instructions P908, applicable for damaged and defective cells and batteries, requires the use of cushioning material: “2. Each inner packaging shall be surrounded by sufficient non-combustible and non-conductive thermal insulation material to protect against a dangerous evolution of heat.” • It is the responsability of the shipper to define the sufficientamount of cushioningmaterial, but no more information is provided. There is a need of practical tests and models to providevalid information to the professionnels shipping batteries and the authorities.

4. 5- Packaging commercial products: road • Some companies are offering strong packagings, validated by their national authorities, for transport of damaged and defective batteries • Example of GRS concept • High cost???

5. 5- Packaging commercial products: road • GRS concept: what is the cost?

6. 5- Packaging commercial products: road • Genius concept: what is the cost?

7. 5- Packaging commercial products: road • Daimler

8. 3- Modeling: model description • Objective: • A simple static thermal model was not sufficient to analyze the results of the testing • The testing was limited to one type and size of battery: there is a need of a model allowing a good prediction of the thermal behavior in case of different battery and packaging sizes or other cushioning materials. • Model description: • A dynamic model has been created: simplified finite elements calculation under Excel, using heat propagation in isotropic spherical conditions through 4 layers of material. • Boundary conditions can be adjusted • Heat source size and layer thickness can be adjusted

9. 3- Modeling: cooling simulation • Using the same parameters defined in the calibrating phase, the runaway phase and the cooling phase were calculated • The initial temperature was set at the level of the material surrounding the cell at the runaway phase start. • The simulation is showing acceptable results for the different layers of the cushioning materials during the cooling phase. Sorbix Absorbant

10. 4- Cushioning calculation: Minimum Safe Distance (MSD) • The « Minimum safe distance » MSD, is the thickness of the cushioning material layer allowing to stop the propagation to the next battery in case of one battery runaway • It has been shown that Li-ion batteries do not release significant amounts of heat up to 100°C ( ref 1). It is then considered that the distance where the cushioning material is heated at 100°C maximum is the  MSD. MSD for a Li-ion 18650 layer • ACCUREC has conducted experiments (ref 1) to measure this MSD with different cushioning materials. • Results obtained with the model are quite comparable to the experiments, except for pyrobubbles: the test result is not in relation to the thermal properties measured in this case.

11. 4- cushioning calculation: simple rules • Proposed quantities: based on the model MSD calculation, a simple geometrical calculation allows to propose the following quantities of cushioning material, respecting the MSD between batteries in an homogeneous mix of batteries and cushioning material: • Many other materials are available. Some have specific properties (i.e. phase transition materials) and may not have the behavior described in this model. • Decision on the best material can be made based on the product cost, the transport cost, or other constraints ( max weight, max volume, process constraints, etc..).

12. 4- cushioning calculation: other cases • Case of Li metal battery: • the model can calculate a minimum value: based on a typical runaway energy of 1300 kJ/kg, the required weight of cushioning material is about the double, compared to the Li-ion. • Nevertheles, this would require some test for validation, particularly for small cells, where the cooling effect of the cushioning material can reduce significantly the thermal runaway energy.

13. 4- cushioning calculation: other cases • Case of large batteries in packaging with limited cushioning: • boundaries conditions of the model adapted:the key parameter is the cooling efficiency of the packaging. • Example of a 100 kg battery surrounded by 7 cm vermiculite thickness in a metallic drum, in conditions allowing the natural convection cooling (i.e. single drum on a pallet). • the max. external temperature is 100°C, and decreases after 5h.

14. 5- Packaging commercial products: air transport • Some companies are offering special materials for packaging and cushionning • FEDEX tests • Liquid coolant was efficient: gel pack placed over the cell, with coated tray to avoid leakage out –no plastic bag-, and with a buffer layer between the gel pack and the cells. The gel pack represents 12/18% of the weight and 20-40% of the batteries volume (1 gel bag on the top of each batteries box). • Even with larger D size Li metal batteries, in some orientations, the gel packs are efficient. • Gel is proprietary ( mixture of coolant and water). Cost under study. => it is a proposed solution. FAA test to stop propagation with water are effective also. • High Cost???

15. Conclusion • the UN regulation on the transport of dangerous goods is aiming at packaging systems avoiding the “dangerous evolution of heat”. • Practical solutions are proposed on the market which can answer the need, but with the risk of a high cost packaging. • It is the interest of the industry to promote the safe transport of the Li batteries: cost efficient solutions should be looked for, tested, and validated by the competent authorities. • Keep Li batteries transport safe !